This application claims priority under 35 U.S.C. xc2xa7xc2xa7119 and/or 365 to 9802344-3 filed in Sweden on Jun. 29, 1998; the entire content of which is hereby incorporated by reference.
The present invention rates to a plus such as an adaptable plug or contact, which can be inserted into a power supply hole device.
There are many portable applications of today such as cellular phones, radios and video games, which are powered or charged from an electrical system of a motor vehicle, such as a car.
It is common practice to insert a plug into the power supply hole device for a cigarette lighter in the motor vehicle, to obtain electrical power from the electrical system of the motor vehicle. However, the diameter of power supply holes varies from car manufacturer to car manufacturer. Inserted plugs loosens, whereby electrical contact failure occurs, for instance due to vibration when driving and the plug must be reinserted. It also occurs that the plugs get stuck in the hole, so they are difficult to get out.
The adapter plugs are designed to fit into different power supply hole devices. The outer dimensions of the cylindrical plug member to be inserted into the tubular power supply hole device are defined of the most narrow power supply hole device in the market and the length of that member is defined by the deepest supply hole. These conditions result in a long and thin plug insertion member.
In the top of this insertion member a tip terminal is situated for electrical connection with the bottom wall contact of the power supply hole device. Often this tip member is coil spring loaded to make the tip terminal flexible in the insertion direction. When the tip terminal is in contact with the bottom wall it is only possible to press the plug further into the hole as deep as the length of the tip terminal allows. The purpose of the tip terminal is to allow the plug to move a short distance backwards from the bottom hole contact without losing the electrical connection with the same. The Tip terminal is designed to fit into shallow tubular power supply hole devices and therefore the tip terminal is, as the insertion member is designed long quite short in length.
The electrical connection with the side wails of the tubular power supply hole device and the gripping and fastening inside the hole is provided by a number of spring contacts means protecting outwardly from the cylindrical member. These contact means are placed quite close the tip terminal. If they were placed in the other end of the insertion member instead there is a risk that the spring contacts never will reach into a shallow hole and the spring contacts will stay outside the hole without any possibility to contact the conducting side wall. However, the tubular inner wall is perforated with recesses, like holes and slits, that could destroy the spring contact means or even be destroyed by the contact means. Said recesses decrease the contact and grip area between the spring contacts and the side-walls and they are positioned closer to the bottom wall than the opening of the power supply hole device The outer area of the inner wall, close to the opening is not perforated and provides the best contact and grip areas in the hole. The known prior art plugs having the spring contact means positioned close to the tip member will only pass said outer area during the insertion.
In the prior art, there are several examples of plugs which can be fitted into holes of different diameters, such as 20, 8-22, 3 mm, without loosening even when exposed to vibration during driving etc, which plugs are also easy to unplug.
EP-A1-550 945 discloses a car plug which can be firmly fitted into a power supply hole device for a cigarette lighter in an automobile, enabling stable electric connection over a long period of time irrespective of the size of the power supply hole device. The car plug has a cylindrical member provided with spring contact means projecting outwardly from the cylindrical member, whereby the projecting spring contact means contact the inner surface of the power supply hole device to obtain electrical contact. It is the power terminal provided on the inner wall of the power supply hole device that presses the terminal in the radial direction, to constitute an electric circuit, when also the tip of the plug is connected to the power provided at the bottom of the power supply hole device.
In this prior art car plug it can be seen that the projecting spring contact means are squeezed and fixed and the electric circuit is obtained when the tip of the tip terminal contacts the power terminal provided at the central bottom of the power supply hole device by a coil spring when forcing the car plug into the power terminal provided at the central bottom of the power supply hole device.
A disadvantage with the prior art plugs is that the force pressing the contact means of the plug to the inner wall of the power supply hole device for powering is quite weak, whereby the plugs might loosen due to vibrations.
As stated above prior an adapter plugs have a number of drawbacks, which result in bad electrical contact, and fastening or gripping into said hole. Not even the above disclosed car plug solves all problems. In prior art, for instance the engagement area is small and the plugs engage deep in holes, whereby the pull-out force can be to low or if the spring terminal grab deep inside the hole where the cut-outs are located this might destroy the power supply insertion hole or the plug, or cause a short circuit.
The present invention relates to an adaptable plug for facilitating firmly fitting into the power supply hole device for a cigarette lighter in a vehicle, such as an automobile, being able to obtain stable electric connection irrespectively of the size of the hole, which plug is also easy to dismount.
The adaptable plug according to the invention increases the forces pressing the contact means against the inner wall of the power supply holy device, by better adaptation to the inner wall of the hole compared to prior art plugs. Therefore, the contact means can also be said to work as xe2x80x9cadaptation meansxe2x80x9d, meaning that besides improved contacting, also the fitting of the plug to the inner wall of the power supply hole device is considerably increased.
Thus, in the following, contact mean are designated xe2x80x9cadaptation meansxe2x80x9d.
When using an adapter plug in a power supply hole device that is shallower than the maximum depth it is designed for, the long insertion member will cause the plug to protrude out of the hole. The more the plug protrudes, the easier it is that the plug will move out of the hole and loose its electrical connection to the bottom wall contact as a result of the car vibrations and chokes.
This problem is solved according to the invention by designing the insertion member of the plug to the shallowest power supply hole device instead of the deepest and the length of the flexible movement of the tip terminal to the difference between the shallowest and the deepest hole. Always insert the whole insertion member and still have god contact with bottom wall contact.
Another problem to be solved is the bad fastening and gripping of the plug into the power supply hole device. This is solved according to the invention by placing the spring contacts means close to the rear end of the insertion member. When the insertion member has been fully inserted in the hole the spring contact means will be positioned on the outer area of the inner wall with the best electrical contact and the best fastening and gripping conditions because there is no recess in said area.
One further problem to be solved is that the design of tie prior art spring contact means is a limitation of the electrical contraction with the inner wall in the hole and the adaptation of the spring contacts means to the radius of the hole. To improve these features a new spring contact means is invented. Said spring contact means will adapt better to the radius of the hole and will work as a sort of electrically conducting adaptation means. This invented adaptation means has an essentially U-shaped cross section perpendicular to the insertion direction. This U-shaped adaptation means has a base and two longish legs or sidewalls extending perpendicular from the base along the two of the opposite base sides. The other two opposite sides, the front end and back end, have no legs. The front end is directed against a top of the insertion member. This construction has a two step adaptation function. The legs of the U-shaped adaptation means is first bent. The magnitude of the force to bend the legs is less than the force to bend the base of the adaptation means. First when the legs is bent as much as possible the base of the adaptation means is bent if necessary.
Yet another problem is to make it easier to insert the plug into the power supply hole device. If the width of the base is increasing from the front of the adaptation means to the back end, this will increase the force needed for inserting the plug during the insertion. When the plug is fully inserted the force needed to pull the plug out of the hole therefore is maximised and the needed pulling force will reduce the more the plug is pulled out of said hole. Said two step adaptation function will also improve the insertion of the plug, In the beginning of the insertion where the base is narrower the legs will be bent. When the plug is fully inserted the base could also have been beat by the force from the inner wall of the hole, especially if the radius is small.
According to a preferred embodiment of the invention, the adaptable plug is designed to be inserted into power supply hole device devices of different depth and radius, each hole device having an inner wall, said plug comprising a grip member and an insertion member, wherein said insertion member comprises a first contact for power connection at the bottom of the hole and an adaptation member having adaptation means for electrical power connection with the inner wall and situated in front of said grip member, wherein said adaptation means is/are separated from said grip member by a ring member, which bears on an opening edge of the power supply hole device and positions the adaptation means alongside with an outer area (OA) of said inner wall when the plug is fully inserted into the power supply hole device.
The adaptable plug is provided with contact means for powering, working radially, thereby grabbing in the inner wall of the hole in at least two points, preferably four points, if two contact means are employed, which increases the friction area in the power supply hole device,
Preferably, the adaptation means, comprising a base and legs is/are essentially U-shaped in cross section, extending in the longitudinal direction of said adaptation member, gripping around said adaptation member by its legs, wherein edges between said legs and base form at least two connection areas, to be brought into contact to the inner wall of said power supply hole device for supplying power to said adaptable plug.
According to yet another embodiment of the invention, the adaptation means operate/-s according to a two step adaptation function, which implies that the insertion of the plug into the hole device the legs are bent as much as possible before the base of the adaptation means is bent.
Preferably, the width in radial direction of said adaptation means is larger than the diameter of the insertion member and the hole, whereby said adaptation member is brought into contact with the inner wall of said power supply hole device, wherein at least two connection areas are obtained.
Preferably, the adaptable plug is adapted to fit holes of a length of 25-40 mm, in particular 28, 5-39 mm.
The adaptable plug does not come off even at intensive vibrations, even if it is fitted in a large hole, and can be fitted into small holes, without implying any problems with dismounting. The adaptable plug fits holes with different diameters, and grabs just inside the hole, where there are no cutouts. Furthermore, the tip of the plug takes up different lengths of holes. An advantage is that the plug does not project a long distance from the hole, to avoid loose fitting. Another advantage is that the adaptation means always grabs where there are no cutouts.